Gas turbines are widely used in industrial and power generation operations. A typical gas turbine includes an axial compressor at the front, one or more combustors around the middle, and a turbine at the rear. Ambient air enters the compressor, and rotating blades and stationary vanes in the compressor progressively impart kinetic energy to the working fluid (air) to produce a compressed working fluid at a highly energized state. The compressed working fluid exits the compressor and flows through nozzles in the combustors where it mixes with fuel and ignites to generate combustion gases having a high temperature, pressure, and velocity. The combustion gases flow to the turbine where they expand to produce work. For example, expansion of the combustion gases in the turbine may rotate a shaft connected to a generator to produce electricity.
It is widely known that the thermodynamic efficiency of a gas turbine increases as the operating temperature, namely the combustion gas temperature, increases. Combustion gas temperatures exceeding 3000° F. are therefore desirable and fairly common in the industry. However, conventional combustion chambers and transition pieces that channel the combustion gases out of the combustor are typically made from materials generally capable of withstanding a maximum temperature on the order of approximately 1500° F. for about 10,000 hours. Therefore, it is desired to provide some form of cooling to the combustion chamber and/or transition piece to protect them from thermal damage.
A variety of techniques are known in the art for providing cooling to the combustion chamber. For example, U.S. Pat. Nos. 5,724,816, 7,010,921, and 7,373,778 assigned to the same assignee as the present invention each describe various structures and methods for cooling a combustor and/or transition piece of a combustor. However, continued improvements in the structures and methods for cooling combustor components would be useful.